U.S. patent application number 17/824201 was filed with the patent office on 2022-09-08 for conversion processing method, printed material production method, and printed material production system.
This patent application is currently assigned to FUJIFILM Corporation. The applicant listed for this patent is FUJIFILM Corporation. Invention is credited to Tomohiro MIZUNO.
Application Number | 20220286582 17/824201 |
Document ID | / |
Family ID | 1000006379031 |
Filed Date | 2022-09-08 |
United States Patent
Application |
20220286582 |
Kind Code |
A1 |
MIZUNO; Tomohiro |
September 8, 2022 |
CONVERSION PROCESSING METHOD, PRINTED MATERIAL PRODUCTION METHOD,
AND PRINTED MATERIAL PRODUCTION SYSTEM
Abstract
There are provided a conversion processing method of performing
LUT conversion processing for converting, via a lookup table (LUT),
texture characteristic information of an object of which texture is
to be reproduced into ink amount information of an ink, which is
used in order to reproduce the object of which texture is to be
reproduced on a medium, the conversion processing method for
optical texture reproduction in which the texture characteristic
information is separated into internal scattering information and
color signal information, the internal scattering information and
the color signal information, which are separated out, are used as
inputs of the LUT conversion processing, and as values of a
modulation transfer function as the internal scattering information
and the color signal information are used in the LUT conversion
processing, reproduction of internal scattering and reproduction of
color reproduction, which are important qualities of texture, can
be simultaneously realized with high accuracy in print production
of performing texture reproduction, a printed material production
method, and a printed material production system.
Inventors: |
MIZUNO; Tomohiro; (Kanagawa,
JP) |
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Applicant: |
Name |
City |
State |
Country |
Type |
FUJIFILM Corporation |
Tokyo |
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JP |
|
|
Assignee: |
FUJIFILM Corporation
Tokyo
JP
|
Family ID: |
1000006379031 |
Appl. No.: |
17/824201 |
Filed: |
May 25, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/JP2020/044283 |
Nov 27, 2020 |
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17824201 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04N 1/6072 20130101;
H04N 1/6019 20130101; H04N 1/6025 20130101 |
International
Class: |
H04N 1/60 20060101
H04N001/60 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 27, 2019 |
JP |
2019-214577 |
Claims
1. A conversion processing method of performing lookup table
conversion processing for converting, via a lookup table, texture
characteristic information of an object of which texture is to be
reproduced into ink amount information of an ink, which is used in
order to reproduce the object of which texture is to be reproduced
on a medium, the conversion processing method comprising:
separating the texture characteristic information into internal
scattering information and color signal information; and using the
internal scattering information and the color signal information,
which are separated out, as inputs of the lookup table conversion
processing, wherein the lookup table conversion processing is
processing of using values of a modulation transfer function as the
internal scattering information and the color signal
information.
2. The conversion processing method according to claim 1, wherein a
value of the modulation transfer function is acquired as the
texture characteristic information, the value of the modulation
transfer function acquired as the texture characteristic
information is separated into a value of the modulation transfer
function as the internal scattering information and a value of the
modulation transfer function as the color signal information, and
the values of the modulation transfer function acquired as the
internal scattering information and the color signal information
are used as input values of the lookup table conversion
processing.
3. The conversion processing method according to claim 1, wherein
the values of the modulation transfer function are acquired as the
internal scattering information and the color signal information,
which are separated out, and the values of the modulation transfer
function acquired as the internal scattering information and the
color signal information are used as input values of the lookup
table conversion processing.
4. The conversion processing method according to claim 1, wherein
the color signal information is color signal information in which
human visual characteristics with respect to lightness, chroma
saturation, and color tone are considered.
5. The conversion processing method according to claim 4, wherein a
signal value of an L*a*b* color space is used as the visual
characteristic.
6. The conversion processing method according to claim 1, wherein
in calculation of an error amount in the lookup table conversion
processing in which a distance from a lattice point of the lookup
table is given, a weight of an error amount of the color signal
information and a weight of an error amount of the internal
scattering information are different from each other.
7. The conversion processing method according to claim 1, wherein
in a ratio between the color signal information and the internal
scattering information, which is a weight of the modulation
transfer function, a weight of the color signal information is
large.
8. The conversion processing method according to claim 7, wherein
the weight of the color signal information is two times or more a
weight of the internal scattering information.
9. A conversion processing method of performing lookup table
conversion processing for converting, via a lookup table, texture
characteristic information of an object of which texture is to be
reproduced into ink amount information of an ink, which is used in
order to reproduce the object of which texture is to be reproduced
on a medium, the method comprising: using, as an input value of the
lookup table conversion processing, a signal value of a perceptual
uniform color space changed from a value of a modulation transfer
function that is internal scattering information and color signal
information, which are included in the texture characteristic
information, in an imaged RGB signal value.
10. The conversion processing method according to claim 9, wherein
the perceptual uniform color space is an L*a*b* color space.
11. The conversion processing method according to claim 1, wherein
the internal scattering information is converted into amounts of
cyan (C), magenta (M), yellow (Y), and black (K) inks and an amount
of a white (W) ink and a scattering amount of a scattering layer
included in the medium through the lookup table conversion
processing.
12. The conversion processing method according to claim 1, wherein
the texture characteristic information is red (R), green (G), and
blue (B) signal values at a plurality of frequencies including zero
frequency, the color signal information is red (R), green (G), and
blue (B) signal values at zero frequency, and the internal
scattering information is red (R), green (G), and blue (B) signal
values at a plurality of frequencies excluding zero frequency.
13. A printed material production method of producing a printed
material obtained by reproducing an object of which texture is to
be reproduced on a medium from texture characteristic information
of the object of which texture is to be reproduced, the printed
material production method comprising: separating the texture
characteristic information into internal scattering information and
color signal information; using values of a modulation transfer
function as the internal scattering information and the color
signal information, which are separated out; performing conversion
into ink amount information of an ink for forming a print layer
obtained by reproducing texture on the medium through lookup table
conversion processing, in which a value of the modulation transfer
function as the internal scattering information and a value of the
modulation transfer function as the color signal information are
used as inputs; and producing the printed material by discharging
the ink on the medium and forming the print layer based on the ink
amount information.
14. A printed material production method of producing a printed
material obtained by reproducing an object of which texture is to
be reproduced on a medium from texture characteristic information
of the object of which texture is to be reproduced, the printed
material production method comprising: changing a value of a
modulation transfer function that is internal scattering
information and color signal information, which are included in the
texture characteristic information, in an imaged RGB signal value
into a signal value of a perceptual uniform color space; performing
conversion into ink amount information of an ink for forming a
print layer obtained by reproducing texture on the medium through
lookup table conversion processing, using the signal value as an
input value; and producing the printed material by discharging the
ink on the medium and forming the print layer based on the ink
amount information.
15. A printed material production system that produces a printed
material obtained by reproducing an object of which texture is to
be reproduced on a medium from texture characteristic information
of the object of which texture is to be reproduced, the printed
material production system comprising: a light scattering measuring
device that acquires the texture characteristic information; a
computer that includes a lookup table, performs lookup table
conversion processing using the lookup table, and converts the
texture characteristic information into ink amount information of
an ink; and a print layer forming device that forms a print layer
by discharging the ink on the medium based on the ink amount
information to produce the printed material, wherein the computer
separates the texture characteristic information acquired by the
light scattering measuring device into internal scattering
information and color signal information, uses values of a
modulation transfer function as the internal scattering information
and the color signal information, which are separated out, and
performs conversion into the ink amount information of the ink for
forming a print layer obtained by reproducing texture on the medium
through the lookup table conversion processing, in which a value of
the modulation transfer function as the internal scattering
information and a value of the modulation transfer function as the
color signal information are used as inputs.
16. A printed material production system that produces a printed
material obtained by reproducing an object of which texture is to
be reproduced on a medium from texture characteristic information
of the object of which texture is to be reproduced, the printed
material production system comprising: a light scattering measuring
device that acquires the texture characteristic information; a
computer that includes a lookup table, performs lookup table
conversion processing using the lookup table, and converts the
texture characteristic information into ink amount information of
an ink; and a print layer forming device that forms a print layer
by discharging the ink on the medium based on the ink amount
information to produce the printed material, wherein the computer
changes values of a modulation transfer function that is internal
scattering information and color signal information, which are
included in the texture characteristic information acquired by the
light scattering measuring device, in imaged red (R), green (G),
and blue (B) signal values into a signal value of a perceptual
uniform color space, and performs conversion into the ink amount
information of the ink for forming a print layer obtained by
reproducing texture on the medium through the lookup table
conversion processing, using the signal value as an input
value.
17. The conversion processing method according to claim 2, wherein
the color signal information is color signal information in which
human visual characteristics with respect to lightness, chroma
saturation, and color tone are considered.
18. The conversion processing method according to claim 2, wherein
in calculation of an error amount in the lookup table conversion
processing in which a distance from a lattice point of the lookup
table is given, a weight of an error amount of the color signal
information and a weight of an error amount of the internal
scattering information are different from each other.
19. The conversion processing method according to claim 2, wherein
in a ratio between the color signal information and the internal
scattering information, which is a weight of the modulation
transfer function, a weight of the color signal information is
large.
20. The conversion processing method according to claim 2, wherein
the internal scattering information is converted into amounts of
cyan (C), magenta (M), yellow (Y), and black (K) inks and an amount
of a white (W) ink and a scattering amount of a scattering layer
included in the medium through the lookup table conversion
processing.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of PCT International
Application No. PCT/JP2020/044283 filed on Nov. 27, 2020, which
claims priority under 35 U.S.C. .sctn. 119(a) to Japanese Patent
Application No. 2019-214577 filed on Nov. 27, 2019. The above
application is hereby expressly incorporated by reference, in its
entirety, into the present application.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present invention relates to a conversion processing
method for optical texture reproduction, a printed material
production method for producing a printed material, such as a
texture reproduced print in which optical texture is reproduced,
and a printed material production system, and particularly to, in
producing a printed material such as a texture reproduced print, a
conversion processing method for optical texture reproduction that
is a data conversion processing technology for simultaneously
improving the accuracy of internal scattering and color
reproduction, which are texture elements, a printed material
production method for producing a printed material such as a
texture reproduced print, in which the accuracy of the internal
scattering and the color reproduction, which are texture elements,
are simultaneously improved and optical texture is reproduced, and
a printed material production system.
2. Description of the Related Art
[0003] In recent years, with the development of a printing
technology, it has become possible to reproduce texture of an
object to be reproduced (hereinafter, simply referred to as an
"object"). For example, with the development of a three-dimensional
(3D) printing technology, the texture (specifically, thickness) of
the object can be reproduced well. In addition, with a technology
of printing using a clear ink (for example, an ultraviolet ray (UV)
ink) having curing properties (hereinafter, referred to as
"2.5-dimensional (2.5D) printing" for convenience), the texture of
the object, particularly, optical texture of the surface of the
object can be reproduced well. Herein, the optical texture
specifically corresponds to an internal scattering characteristic
of light.
[0004] As described above, with the recent development of the 3D
printing technology or the 2.5D (thick) printing technology, there
has been a high sense of expectation that texture which has not
been able to be realized in two-dimensional (2D) printing of the
related art will be reproduced as a printed object.
[0005] For this reason, various proposals for reproducing the
texture of the object have been made (see JP2016-144005A and
Control of translucency by UV printing on translucent
material/Report by the Information Processing Society of Japan,
Vol.2018-CG-169/No.10 2018/3/3).
[0006] JP2016-144005A proposes an image processing device and an
image processing method in which texture reproduction processing
for reproducing the texture of the object is performed.
[0007] In the technology disclosed in JP2016-144005A, texture data
including at least color information and gloss information of an
object to be reproduced is input, based on a texture reproduction
range of a texture reproduction device, the gloss information is
mapped to a gloss reproduction range, the color information is
mapped to a color reproduction range with the gloss information
after mapping maintained, and an output signal to be output to the
texture reproduction device is generated based on the texture data
indicated by the color information and the gloss information after
mapping.
[0008] In this manner, in the technology disclosed in
JP2016-144005A, a mismatch between the texture of the object to be
reproduced and the texture reproduction range is eliminated, and a
reproduced object in which the texture of the object is more
appropriately reproduced can be obtained.
[0009] In addition, Control of translucency by UV printing on
translucent material/Report by the Information Processing Society
of Japan, Vol.2018-CG-169/No.10 2018/3/3 proposes an image
processing device and an image processing method in which texture
reproduction processing for reproducing the texture of the object
is performed.
[0010] In the technology disclosed in Control of translucency by UV
printing on translucent material/Report by the Information
Processing Society of Japan, Vol.2018-CG-169/No.10 2018/3/3, a
method of controlling the translucency (optical texture) of a
printed material by using a layer structure of a translucent
material and an ultraviolet (UV) ray hardened ink without printing
the white background is proposed. In the technology disclosed in
Control of translucency by UV printing on translucent
material/Report by the Information Processing Society of Japan,
Vol.2018-CG-169/No.10 2018/3/3, in order to express translucency,
the modulation transfer function (MTF) is used, MTFs of a
translucent material, a UV ink, and a printed material are
projected from a projector at a plurality of different spatial
frequencies, and reflected light is measured by imaging with a red
(R), green (G), and blue (B) camera. In translucency reproduction,
based on the measurement, a lookup table (LUT) related to a
combination of factors, such as types and overlapping numbers of
translucent materials and UV inks, and translucency, is organized,
the LUT is searched in an output system, and a combination of
factors for realizing required translucency is determined
[0011] In this manner, what is currently being examined is to
perform processing of converting an MTF characteristic into the
amounts of cyan (C), magenta (M), yellow (Y), and white (W) inks
via the LUT in which internal scattering viewed from red (R), green
(G), and blue (B) channels is considered.
[0012] For example, as shown in FIG. 20, first, projection light at
a plurality (six types, in the shown example) of different spatial
frequencies is projected onto RGB color patches 50, the reflected
light is observed to perform MTF measurement, and MTF data of the
RGB channels represented by six types of MTF color patches 54 is
obtained. Next, the MTF data of the RGB channels obtained in this
manner is LUT-converted, and data of the amounts of CMYW inks
represented by a color patch 70 is obtained. A reproduced color
patch print 72 obtained by reproducing the color patch 50 is
printed out using the data of the amounts of CMYW inks obtained in
this manner.
[0013] Therefore, for example, from a texture reproduction sample
52 that is an original image, which is an image of marble, a
reproduced image print 74 can be obtained by similarly performing
MTF measurement, LUT conversion, and printing out.
SUMMARY OF THE INVENTION
[0014] However, in the technology disclosed in JP2016-144005A,
since gloss to be reproduced is determined from the gloss
reproduction range of the texture reproduction device and then the
texture reproduction device determines a color to be reproduced
from the color reproduction range that can be reproduced with the
gloss maintained, in a case of a printed material in which a gloss
difference between an object and a reproduced object greatly
affects visual impression, the gloss of the object can be
reproduced well, but there is a problem that a color error is
remarkably visible because colors in a case of being viewed by a
human are not sufficiently considered.
[0015] In addition, in the technology disclosed in Control of
translucency by UV printing on translucent material/Report by the
Information Processing Society of Japan, Vol.2018-CG-169/No.10
2018/3/3, an LUT for converting the MTF of the RGB channels into
the amounts of cyan (C), magenta (M), yellow (Y), and UV (U) inks
is used. As described above, there is an unavoidable error in the
conversion of the characteristics of the natural world using the
LUT consisting of a finite number of inks and a finite amount of
ink. For this reason, there is a problem that a color error is
remarkably visible in some cases since human visual
characteristics, particularly a color difference in a case of being
viewed by a human are not considered.
[0016] What is currently being examined is, including the examples
shown in Control of translucency by UV printing on translucent
material/Report by the Information Processing Society of Japan,
Vol.2018-CG-169/No.10 2018/3/3 and FIG. 20, performing processing
of converting an MTF characteristic into the amounts of CMYU inks
via an LUT in which internal scattering viewed in the RGB channels
is considered. For this reason, in the printed material, such as a
circled region 72a of the reproduced color patch print 72 shown in
FIG. 20 and the reproduced image print 74, there are problems that
color reproduction, which is an important element of texture, is
not sufficiently reproduced, graininess is poor, and particularly
granular feeling (roughness), grayscale inversion, and/or tone jump
is generated.
[0017] As shown in FIG. 15, in a case of approximating the MTF in
the printed material with respect to a graph of a target MTF, which
is close to the intensity of 1 in a period 0, has decreasing
intensity as going toward high frequencies, and is indicated by a
solid line, a nearest MTF in the LUT is selected in LUT conversion.
Thus, an approximate MTF by an ink indicated by a dotted line which
is substantially constant at the intensity of approximately 0.5
from the period 0 to a high frequency is selected.
[0018] However, in the graph of the MTF, an error of intensity in
the period 0 representing an average ink color is large as 0.5, the
error with respect to the ink average color is large, and a color
difference is remarkably visible.
[0019] The present invention is devised in view of such
circumstances and an object thereof is to provide a conversion
processing method for optical texture reproduction, in which
reproduction of internal scattering and reproduction of color
reproduction, which are important qualities of texture, can be
simultaneously realized with high accuracy in print production of
performing texture reproduction, a printed material production
method, in which a printed material, such as a texture reproduced
print in which optical texture is reproduced with the accuracy of
internal scattering and color reproduction, which are texture
elements, simultaneously improved, can be produced, and a printed
material production system.
[0020] In order to achieve the object, according to a first aspect
of the present invention, there is provided a conversion processing
method of performing lookup table conversion processing for
converting, via a lookup table, texture characteristic information
of an object of which texture is to be reproduced into ink amount
information of an ink, which is used in order to reproduce the
object of which texture is to be reproduced on a medium, the
conversion processing method including separating the texture
characteristic information into internal scattering information and
color signal information, and using the internal scattering
information and the color signal information, which are separated
out, as inputs of the lookup table conversion processing, in which
the lookup table conversion processing is processing of using
values of a modulation transfer function as the internal scattering
information and the color signal information.
[0021] In order to achieve the object, according to a second aspect
of the present invention, there is provided a printed material
production method of producing a printed material obtained by
reproducing an object of which texture is to be reproduced on a
medium from texture characteristic information of the object of
which texture is to be reproduced, the printed material production
method including separating the texture characteristic information
into internal scattering information and color signal information,
using values of a modulation transfer function as the internal
scattering information and the color signal information, which are
separated out, performing conversion into ink amount information of
an ink for forming a print layer obtained by reproducing texture on
the medium through lookup table conversion processing, in which a
value of the modulation transfer function as the internal
scattering information and a value of the modulation transfer
function as the color signal information are used as inputs, and
producing the printed material by discharging the ink on the medium
and forming the print layer based on the ink amount
information.
[0022] In order to achieve the object, according to a third aspect
of the present invention, there is provided a printed material
production system that produces a printed material obtained by
reproducing an object of which texture is to be reproduced on a
medium from texture characteristic information of the object of
which texture is to be reproduced, the printed material production
system including a light scattering measuring device that acquires
the texture characteristic information, a computer that includes a
lookup table, performs lookup table conversion processing using the
lookup table, and converts the texture characteristic information
into ink amount information of an ink, and a print layer forming
device that forms the print layer by discharging the ink on the
medium based on the ink amount information to produce the printed
material, in which the computer separates the texture
characteristic information acquired by the light scattering
measuring device into internal scattering information and color
signal information, uses values of a modulation transfer function
as the internal scattering information and the color signal
information, which are separated out, and performs conversion into
the ink amount information of the ink for forming a print layer
obtained by reproducing texture on the medium through the lookup
table conversion processing, in which a value of the modulation
transfer function as the internal scattering information and a
value of the modulation transfer function as the color signal
information are used as inputs.
[0023] In the first to third aspects, it is preferable that a value
of the modulation transfer function is acquired as the texture
characteristic information, the value of the modulation transfer
function acquired as the texture characteristic information is
separated into a value of the modulation transfer function as the
internal scattering information and a value of the modulation
transfer function as the color signal information, and the values
of the modulation transfer function acquired as the internal
scattering information and the color signal information are used as
input values of the lookup table conversion processing.
[0024] Alternatively, it is preferable that the values of the
modulation transfer function are acquired as the internal
scattering information and the color signal information, which are
separated out, and the values of the modulation transfer function
acquired as the internal scattering information and the color
signal information are used as input values of the lookup table
conversion processing.
[0025] It is preferable that the color signal information is color
signal information in which human visual characteristics with
respect to lightness, chroma saturation, and color tone are
considered.
[0026] In addition, it is preferable that a signal value of an
L*a*b* color space is used as the visual characteristic.
[0027] In addition, it is preferable that in calculation of an
error amount in the lookup table conversion processing in which a
distance from a lattice point of the lookup table is given, a
weight of an error amount of the color signal information and a
weight of an error amount of the internal scattering information
are different from each other.
[0028] In addition, it is preferable that in a ratio between the
color signal information and the internal scattering information,
which is a weight of the modulation transfer function, a weight of
the color signal information is large.
[0029] In addition, it is preferable that the weight of the color
signal information is two times or more a weight of the internal
scattering information.
[0030] In order to achieve the object, according to a fourth aspect
of the present invention, there is provided a conversion processing
method of performing lookup table conversion processing for
converting, via a lookup table, texture characteristic information
of an object of which texture is to be reproduced into ink amount
information of an ink, which is used in order to reproduce the
object of which texture is to be reproduced on a medium, the method
including using, as an input value of the lookup table conversion
processing, a signal value of a perceptual uniform color space
changed from a value of a modulation transfer function that is
internal scattering information and color signal information, which
are included in the texture characteristic information, in an
imaged RGB signal value.
[0031] In order to achieve the object, according to a fifth aspect
of the present invention, there is provided a printed material
production method of producing a printed material obtained by
reproducing an object of which texture is to be reproduced on a
medium from texture characteristic information of the object of
which texture is to be reproduced, the printed material production
method including changing a value of a modulation transfer function
that is internal scattering information and color signal
information, which are included in the texture characteristic
information, in an imaged RGB signal value into a signal value of a
perceptual uniform color space, performing conversion into ink
amount information of an ink for forming a print layer obtained by
reproducing texture on the medium through lookup table conversion
processing, using the signal value as an input value, and producing
the printed material by discharging the ink on the medium and
forming the print layer based on the ink amount information.
[0032] In order to achieve the object, according to a sixth aspect
of the present invention, there is provided a printed material
production system that produces a printed material obtained by
reproducing an object of which texture is to be reproduced on a
medium from texture characteristic information of the object of
which texture is to be reproduced, the printed material production
system including a light scattering measuring device that acquires
the texture characteristic information, a computer that includes a
lookup table, performs lookup table conversion processing using the
lookup table, and converts the texture characteristic information
into ink amount information of an ink, and a print layer forming
device that forms the print layer by discharging the ink on the
medium based on the ink amount information to produce the printed
material, in which the computer changes values of a modulation
transfer function that is internal scattering information and color
signal information, which are included in the texture
characteristic information acquired by the light scattering
measuring device, in imaged RGB signal values into a signal value
of a perceptual uniform color space, and performs conversion into
the ink amount information of the ink for forming a print layer
obtained by reproducing texture on the medium through the lookup
table conversion processing, using the signal value as an input
value.
[0033] In the fourth to sixth aspects, it is preferable that the
perceptual uniform color space is an L*a*b* color space.
[0034] In the first to sixth aspects, it is preferable that the
internal scattering information is converted into amounts of cyan
(C), magenta (M), yellow (Y), and black (K) inks and an amount of a
white (W) ink and a scattering amount of a scattering layer
included in the medium through the lookup table conversion
processing.
[0035] In addition, it is preferable that the texture
characteristic information is red (R), green (G), and blue (B)
signal values at a plurality of frequencies including zero
frequency, the color signal information is red (R), green (G), and
blue (B) signal values at zero frequency, and the internal
scattering information is red (R), green (G), and blue (B) signal
values at a plurality of frequencies excluding zero frequency.
[0036] With the present invention, in print production of
performing texture reproduction, the reproduction of internal
scattering and the reproduction of color reproduction, which are
important qualities of texture, can be simultaneously realized with
high accuracy.
[0037] With the present invention, a printed material such as a
texture reproduced print, in which optical texture is reproduced
with the accuracy of internal scattering and color reproduction,
which are texture elements, simultaneously improved, can be
produced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 is a configuration diagram showing a configuration of
a print system that executes a conversion processing method
according to an embodiment of the present invention.
[0039] FIG. 2 is a schematic diagram showing an internal scattering
phenomenon of light.
[0040] FIG. 3 is a schematic diagram showing a configuration of a
texture reproduced print.
[0041] FIG. 4 is a schematic diagram showing a configuration of a
print layer forming device shown in FIG. 1.
[0042] FIG. 5 is a diagram showing a nozzle surface of an ink
discharging mechanism included in the print layer forming device
shown in FIG. 4.
[0043] FIG. 6 is a diagram showing a sample pattern.
[0044] FIG. 7 is a diagram showing a rectangular wave chart.
[0045] FIG. 8 is a graph showing an example of MTF data.
[0046] FIG. 9 is a diagram showing an example of a flow of LUT
conversion processing using a texture reproduction conversion LUT
used in the present invention.
[0047] FIG. 10 is a flowchart showing an example of conversion LUT
creation processing of creating the texture reproduction conversion
LUT used in the present invention.
[0048] FIG. 11 is a flowchart showing an example of a flow of light
scattering estimation processing shown in FIG. 10.
[0049] FIG. 12 is a diagram showing an example of a processing flow
of texture reproduced print production in which the conversion
processing method of the embodiment of the present invention is
executed.
[0050] FIG. 13 is a diagram showing another example of the
processing flow of the texture reproduced print production in which
the conversion processing method of the embodiment of the present
invention is executed.
[0051] FIG. 14 is an example of a graph of an MTF showing an LUT
using method in the conversion processing method for optical
texture reproduction of the embodiment of the present
invention.
[0052] FIG. 15 is a graph of an MTF showing an LUT using method of
the related art for optical texture reproduction.
[0053] FIG. 16 is an example of a graph showing an MTF.
[0054] (A) of FIG. 17 is an example of a graph showing an MTF in a
frequency space, and (B) of FIG. 17 is an example of a graph
showing a point spread function (PSF) in a real space.
[0055] FIG. 18 is an example of a graph showing two MTFs having
almost the same half-width.
[0056] FIG. 19 is another example of a graph showing two MTFs
having almost the same half-width.
[0057] FIG. 20 is a diagram showing a processing flow in an optical
texture reproduction method of the related art.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0058] A conversion processing method for optical texture
reproduction according to embodiments of the present invention will
be described in detail below based on suitable embodiments shown in
the accompanying drawings.
[0059] The embodiments to be described below are merely examples
given in order to facilitate understanding of the present
invention, and are not to limit the present invention. That is, the
present invention is not limited without departing from the gist
thereof, and can be changed or improved from the embodiments to be
described below. In addition, it is evident that the present
invention includes the equivalent thereof.
[0060] In addition, in the present specification, a numerical range
represented by using "to" means a range including numerical values
before and after "to" as a lower limit value and an upper limit
value.
[0061] In addition, in the present specification, unless stated
otherwise, a lamination direction of a print layer to be described
later will be defined as an up-and-down direction, a side closer to
a medium will be defined as "lower side", and a side further from
the medium will be defined as "upper side".
Outline of Present Invention
[0062] There is provided a conversion processing method for optical
texture reproduction according to a first embodiment of the present
invention, of performing lookup table (hereinafter, referred to as
LUT) conversion processing for converting, via an LUT, texture
characteristic information of an object of which texture is to be
reproduced into ink amount information of an ink, which is used in
order to reproduce the object of which texture is to be reproduced
on a medium, the conversion processing method including separating
the texture characteristic information into internal scattering
information and color signal information, and using the internal
scattering information and the color signal information, which are
separated out, as inputs of the LUT conversion processing, in which
the LUT conversion processing is processing of using values of a
modulation transfer function (hereinafter, referred to as MTF) as
the internal scattering information and the color signal
information.
[0063] There is provided a conversion processing method for optical
texture reproduction according to a second embodiment of the
present invention, of performing LUT conversion processing for
converting, via an LUT, texture characteristic information of an
object of which texture is to be reproduced into ink amount
information of an ink, which is used in order to reproduce the
object of which texture is to be reproduced on a medium, the method
including using, as an input value of the LUT conversion
processing, a signal value of a perceptual uniform color space
changed from a value of an MTF that is internal scattering
information and color signal information, which are included in the
texture characteristic information, in an imaged RGB signal
value.
[0064] In the conversion processing method according to the first
and second embodiments of the present invention, optical texture
reproduction that is more excellent than in the technology of the
related art described above is possible in that a conversion LUT,
in which a color difference in a case of being viewed by a human is
considered, is used.
[0065] The conversion processing method of the embodiments of the
present invention is used in order to produce a printed material in
which the optical texture, for example, surface texture of the
object of which texture is to be reproduced is reproduced, that is,
a printed object produced using an ink. For example, the conversion
processing method can be used in producing a printed material
(printed object) having both of internal scattering and color
reproduction with high accuracy as in 3D printing and 2.5D printing
for reproducing texture (printing of laminating inks).
[0066] The conversion processing method of the embodiment of the
present invention realizes texture by internal scattering that
cannot be realized in 2D printing of the related art and
demonstrates an effect in which image quality degradation that is
caused by partial fluctuations in color information, such as
grayscale inversion and/or graininess or color shift, and that
aggravates by performing texture reproduction, in which visual
characteristics with respect to color information are not
considered in a image quality, which is an important item in terms
of image quality in the related art, can be reduced.
[0067] In addition, the conversion processing method of the
embodiment of the present invention demonstrates another effect of
performing reproduction in which a texture item that emphasizes
reproduction according to the purpose is selected by separating
internal scattering information and color reproduction information
from each other.
[0068] Further, the conversion processing method of the embodiment
of the present invention demonstrates still another effect of
producing a printed material (printed object) on which texture
processing is performed through processing of emphasizing internal
scattering more than the reality, in addition to the object of
faithful reproduction.
[0069] There is provided a printed material production method
according to a third embodiment of the present invention, of
producing a printed material obtained by reproducing an object of
which texture is to be reproduced on a medium from texture
characteristic information of the object of which texture is to be
reproduced, the printed material production method including
separating the texture characteristic information into internal
scattering information and color signal information, using values
of an MTF as the internal scattering information and the color
signal information, which are separated out, performing conversion
into ink amount information of an ink for forming a print layer
obtained by reproducing texture on the medium through LUT
conversion processing, in which a value of the modulation transfer
function as the internal scattering information and a value of the
MTF as the color signal information are used as inputs, and
producing the printed material by discharging the ink on the medium
and forming the print layer based on the ink amount
information.
[0070] There is provided a printed material production method
according to a fourth embodiment of the present invention, of
producing a printed material obtained by reproducing an object of
which texture is to be reproduced on a medium from texture
characteristic information of the object of which texture is to be
reproduced, the printed material production method including
changing a value of an MTF that is internal scattering information
and color signal information, which are included in the texture
characteristic information, in an imaged RGB signal value into a
signal value of a perceptual uniform color space, performing
conversion into ink amount information of an ink for forming a
print layer obtained by reproducing texture on the medium through
LUT conversion processing, using the signal value as an input
value, and producing the printed material by discharging the ink on
the medium and forming the print layer based on the ink amount
information.
[0071] There is provided a printed material production system
according to a fifth embodiment of the present invention that
produces a printed material obtained by reproducing an object of
which texture is to be reproduced on a medium from texture
characteristic information of the object of which texture is to be
reproduced, the printed material production system including a
light scattering measuring device that acquires the texture
characteristic information, a computer that includes an LUT,
performs LUT conversion processing using the LUT, and converts the
texture characteristic information into ink amount information of
an ink, and a print layer forming device that forms the print layer
by discharging the ink on the medium based on the ink amount
information to produce the printed material, in which the computer
separates the texture characteristic information acquired by the
light scattering measuring device into internal scattering
information and color signal information, uses values of an MTF as
the internal scattering information and the color signal
information, which are separated out, and performs conversion into
the ink amount information of the ink for forming a print layer
obtained by reproducing texture on the medium through the LUT
conversion processing, in which a value of the MTF as the internal
scattering information and a value of the MTF as the color signal
information are used as inputs.
[0072] There is provided a printed material production system
according to a sixth embodiment of the present invention that
produces a printed material obtained by reproducing an object of
which texture is to be reproduced on a medium from texture
characteristic information of the object of which texture is to be
reproduced, the printed material production system including a
light scattering measuring device that acquires the texture
characteristic information, a computer that includes an LUT,
performs LUT conversion processing using the LUT, and converts the
texture characteristic information into ink amount information of
an ink, and a print layer forming device that forms the print layer
by discharging the ink on the medium based on the ink amount
information to produce the printed material, in which the computer
changes values of an MTF that is internal scattering information
and color signal information, which are included in the texture
characteristic information acquired by the light scattering
measuring device, in imaged RGB signal values into a signal value
of a perceptual uniform color space, and performs conversion into
the ink amount information of the ink for forming a print layer
obtained by reproducing texture on the medium through the LUT
conversion processing, using the signal value as an input
value.
[0073] The printed material production method according to the
third embodiment of the present invention and the printed material
production system according to the fifth embodiment of the present
invention execute the conversion processing method according to the
first embodiment of the present invention, and the printed material
production method according to the fourth embodiment of the present
invention and the printed material production system according to
the sixth embodiment of the present invention execute the
conversion processing method according to the second embodiment of
the present invention.
[0074] The printed material production method and the printed
material production system according to the embodiments of the
present invention can produce the printed material in which the
optical texture, for example, surface texture of the object of
which texture is to be reproduced is reproduced, that is, the
printed object produced using the ink, for example, the printed
material (printed object) having both of internal scattering and
color reproduction with high accuracy as in 3D printing and 2.5D
printing (printing of laminating inks) for reproducing texture.
[0075] The printed material production method and system of the
embodiments of the present invention demonstrate the same effects
as in the conversion processing method of the embodiments of the
present invention.
Configuration of Print System That Executes Conversion Processing
Method of Present Invention
[0076] First, a printed material production system that executes
the conversion processing method for optical texture reproduction
according to the embodiment of the present invention, that is, a
configuration of the print system will be described.
[0077] FIG. 1 is a configuration diagram showing the configuration
of the print system that executes the conversion processing method
according to the embodiment of the present invention.
[0078] A print system 10 shown in FIG. 1 is a facility that
reproduces optical texture of an object of which texture is to be
reproduced 12 and in a strict sense, produces a texture reproduced
print 18 obtained by reproducing the optical texture on a medium 14
using an ink 16.
Object of Which Texture is to Be Reproduced
[0079] First, in the present invention, the "object of which
texture is to be reproduced" 12 is a member which is a target of
texture reproduction and hereinafter, will also be simply referred
to as the object 12. Examples of the object include a material
having surface texture (in a strict sense, optical texture) that is
different depending on a part and specifically include natural
materials such as rocks, including marble and granite, stones,
wood, hair, bones, skin, teeth, cotton, and silk.
[0080] That is, the conversion processing method of the embodiment
of the present invention is particularly useful in printing in
which texture of a thing having internal scattering is reproduced,
such as stone materials, including marble, skin, and teeth.
[0081] Hereinafter, although marble is considered as a typical
example of the object 12, it is evident that other materials may be
used as the object 12.
[0082] In addition, in the present invention, "texture" is optical
texture, and "texture characteristic information" has, for example,
internal scattering information represented by light scattering and
color signal information.
[0083] Light scattering representing internal scattering
information is an internal scattering characteristic (also referred
to as subsurface scattering) of light. Internal scattering is, in a
case where a thing is irradiated with light, emission of the light
from a position separated from a light incidence position to the
surface of the thing as the light repeats reflection and scattering
inside the thing as shown in FIG. 2. In addition, an internal
scattering characteristic of light is identified based on a
distance (a distance d shown in FIG. 2) from the light incidence
position to an emission position and intensity of the light at the
emission position. Light scattering data is represented as internal
scattering information.
[0084] Insofar as the color of the object 12 can be expressed,
color signal information may be any information or may be various
signal values of a color space. For example, the color signal
information may be three primary colors of light consisting of red
(R), green (G), and blue (B). In addition, the color signal
information is preferably color signal information in which human
visual characteristics with respect to three attributes of colors,
including lightness, chroma saturation, and color tone, are
considered, and in this case, signal values of the L*a*b* color
space standardized by the International Commission on Illumination
(CIE) in 1976 are preferably used as visual characteristics. In
addition, the color signal information may be a signal value of a
perceptual uniform color space. In this case, it is preferable that
the perceptual uniform color space is the L*a*b* color space.
Texture Reproduced Print
[0085] In addition, in the present invention, the "texture
reproduced print" 18 is a printed material obtained by reproducing
the optical texture of the object 12 on the surface of the medium
14 using the ink 16. On the surface of the texture reproduced print
18 (a surface on a visible side), the surface texture of the object
12, that is, colors, light scattering, and patterns are
reproduced.
[0086] Executing the conversion processing method of the embodiment
of the present invention is executing texture reproduced printing
of forming a print layer 17 consisting of the ink 16 on the medium
14 in order to reproduce the surface texture of the object 12
described above. Through the texture reproduced printing, the
texture reproduced print 18 shown in FIG. 3 is produced. In FIG. 3,
a configuration of the texture reproduced print 18 is schematically
shown, and for convenience of illustration, the thickness and size
of each portion are different from the actual content.
[0087] As shown in FIG. 3, the texture reproduced print 18 is
composed of the medium 14 and the print layer 17 formed on the
surface (print surface) of the medium 14.
Medium
[0088] The "medium" 14 is a substrate for the texture reproduced
print 18 shown in FIG. 3, is a texture reproduced printing
substrate, and has light scattering. The medium 14 used in texture
reproduction printing is the medium 14 for texture reproduction
printing.
[0089] The medium 14 for texture reproduction is a laminate
composed of a thin plate-shaped internal scattering member 14b
being laminated on white paper, which is a white medium 14a.
[0090] The internal scattering member 14b is a layer having light
scattering in the medium 14. Therefore, by having the internal
scattering member 14b having different light scattering, the medium
14 have different light scattering.
[0091] Herein, the internal scattering member 14b is a translucent
(for example, semi-dull color or milky-white color)
light-transmitting member and is a member of which a difference
between total light transmittance and scattered light transmittance
is 0% to 10%. Specific examples of the internal scattering member
14b include a milky-white or white acrylic plate and a substrate
used in inkjet printing using a ultraviolet curable ink, such as a
vinyl chloride material and a polyethylene terephthalate (PET)
material. As the internal scattering member 14b, a member having
total light transmittance of 10% to 80% or less and transmitted
light transmittance of 10% to 80% is preferable. In addition, for
the internal scattering member 14b, a Haze value is preferably 1 to
90%, and more preferably, the Haze value may be 30 to 60%.
[0092] Although the thickness of each portion of the internal
scattering member 14b is homogeneous in the present embodiment,
without being limited thereto, the thickness of each portion of the
internal scattering member 14b may be changed without being
homogeneous.
[0093] On the other hand, white paper, which is the white medium
14a, configures a lowermost layer of the texture reproduced print
18. The white medium 14a is closely attached to the internal
scattering member 14b and is adhered to, for example, the surface
of the internal scattering member 14b. However, the white medium
14a is not limited to a case of being adhered to the internal
scattering member 14b and may be in contact with the internal
scattering member 14b. In addition, it is preferable to set the
white medium 14a such that light reflectivity is highest in the
texture reproduced print 18 and the reflectivity is 90% or more. In
addition, the white medium 14a is not limited to white paper, and
it is possible to use a white sheet, a film, a plate material, a
fiber body (cloth), and a plastic substrate (for example, an
acrylic material, polyethylene terephthalate (PET), and a vinyl
chloride material) instead.
[0094] The medium 14 for texture reproduction is not limited to the
substrate having the white medium 14a and the internal scattering
member 14b and may be, for example, the internal scattering member
14b alone or may be a medium having a member other than the white
medium 14a and the internal scattering member 14b. In addition,
although the thickness of each portion of the white medium 14a is
homogeneous in the present embodiment, without being limited
thereto, the thickness of each portion of the white medium 14a may
be changed without being homogeneous.
[0095] The print layer 17 consists of a multilayer structure in
which layers of inks landed (adhered) on the surface of the medium
14, which is a print surface, are laminated. In addition, the print
layer 17 is formed on the print surface of the medium 14 based on
data (specifically, color signal information and internal
scattering information to be described later) related to the
surface texture of the object 12.
Ink
[0096] Examples of the "ink" 16 used in the present invention
include three color inks, including cyan (C), magenta (M), and
yellow (Y), which are color fluids, a black (K) ink, which is a
black fluid, and a white (W) ink, which is a white fluid, but a
clear ink, which is a transparent fluid, may be used in addition
thereto. The clear ink is not always used in order to form the
print layer 17 in the present invention, but the clear ink can be
used insofar as the clear ink is effective in reproducing the
optical texture.
[0097] Herein, the color ink is a general ink that contains a
colored pigment or dye and is used in color printing. The black ink
is a black ink that contains carbon black at a high concentration.
The white ink is a white ink that contains a white pigment or
scatterer and is used in, for example, underprinting. The clear ink
is an ultraviolet ray hardening fluid that hardens by receiving
light (specifically, ultraviolet rays). The clear ink may be a
transparent fluid that can be hardened by irradiation with light.
In addition, examples of irradiation light include ultraviolet
rays, infrared rays, and visible rays.
[0098] In addition, in the present invention, a range of the print
surface, in which the print layer 17 is formed, is divided into a
plurality of unit regions, and the print layer 17 is formed in an
image-wise manner according to the position of each unit region as
shown in FIG. 3. Accordingly, texture reproduced on the texture
reproduced print 18 changes according to each portion of the
texture reproduced print 18. In other words, texture at each
portion of the texture reproduced print 18 is determined by a
structure (layer structure) in each portion in the print layer
17.
[0099] Herein, a unit region, which is a unit in a case of dividing
the range of the print surface, in which the print layer 17 is
formed, is a minute rectangular region and is a split region set in
a case of defining light scattering of an object. To describe more
specifically, the unit region is, for example, in a case of
measuring light scattering using a camera, a region set in a size
corresponding to resolution (pixels) in a case of imaging the
surface of the object 12 with the camera or a wider sized region
obtained by averaging the size.
[0100] To describe the print layer 17 specifically, as shown in
FIG. 3, at a part 1a of the texture reproduced print 18, a white
layer 17b is disposed on the surface (internal scattering member
14b) of the medium 14, and a color layer 17a is disposed thereon as
an outermost layer of the print layer 17. The print layer 17 has a
two-layer structure including the white layer 17b and the color
layer 17a. The color layer 17a is an ink layer composed of three
colors of YMC inks and a black (K) ink. The white layer 17b is an
ink layer composed of a white (W) ink.
[0101] Next, at a part 1b of the texture reproduced print 18, only
the white layer 17b is disposed on the internal scattering member
14b of the medium 14, and the white layer 17b is disposed on the
outermost layer of the print layer 17.
[0102] In addition, at a part 1c of the texture reproduced print
18, only the color layer 17a is disposed on the internal scattering
member 14b of the medium 14, and the color layer 17a is disposed on
the outermost layer of the print layer 17.
[0103] Such a white layer 17b is disposed in the print layer 17 at
a position according to texture characteristic information
(specifically, color signal information and internal scattering
information) related to the surface texture of the object 12. To
describe specifically, forming conditions of the print layer 17 is
set based on the two types of information, and as a result of
forming the print layer 17 in accordance with the forming
conditions, the white layer 17b is disposed in an image-wise manner
in the print layer 17.
[0104] To describe in more detail with reference to FIG. 3, at the
part la of the texture reproduced print 18, which corresponds to a
color portion, the white layer 17b is disposed between the color
layer 17a and the internal scattering member 14b of the medium 14,
and the white layer 17b is adjacent to the color layer 17a
immediately below the color layer 17a as shown in FIG. 3. By
providing the white layer 17b immediately below the color layer 17a
as described above, light incident from above the color layer 17a
is reflected from the white layer 17b after the color layer 17a
transmits the light. Accordingly, the light which has passed
through the color layer 17a can be relatively clearly seen by a
viewer by being efficiently reflected, without being scattered and
absorbed. Accordingly, at the part la corresponding to the colored
portion, for example, in a case where light incident thereto is
reflected at a position separated from the incidence position due
to internal scattering, light scattering having a not so long
distance between the incidence position and the reflected position
is reproduced.
[0105] In the configuration of the part 1a of FIG. 3, the effect of
internal scattering changes according to the thickness of the white
layer 17b. That is, as the thickness of the white layer 17b
increases, light does not go to the layer of the medium 14, and
spread caused by internal scattering decreases. On the contrary, as
the thickness of the white layer 17b decreases, the spread of the
light caused by internal scattering affected by the layer of the
medium 14 increases.
[0106] In addition, at the part 1b of the texture reproduced print
18, in which there is no color portion, the white layer 17b is
disposed as the outermost layer on the medium 14. By providing the
white layer 17b as the outermost layer as described above, light
reflection is visible more clearly.
[0107] Further, at the part 1c of the texture reproduced print 18,
in which there is only the color portion, the color layer 17a is
disposed as the outermost layer on the internal scattering member
14b of the medium 14. By providing the color layer 17a as the
outermost layer on the internal scattering member 14b, light
incident from above the color layer 17a is incident to the internal
scattering member 14b after the color layer 17a transmits the
light. Thus, the light is scattered and absorbed in the internal
scattering member 14b. Accordingly, for example, in a case where
light incident thereto is reflected at a position separated from
the incidence position due to internal scattering, relatively
strong light scattering having a long distance between the
incidence position and the reflected position to some extent is
reproduced.
[0108] In the present invention, texture may be controlled by
disposing a black layer made by a K ink in a underlayer of the
white layer 17b or disposing a transparent layer made by a clear
ink in the underlayer layer thereof.
Print System
[0109] Next, hereinafter, the print system 10 will be
described.
[0110] As shown in FIG. 1, the print system 10 has a light
scattering measuring device 20, a computer 30, and a print layer
forming device 40 as main configuration devices and produces the
texture reproduced print 18 from the object of which texture is to
be reproduced 12 as described above.
[0111] Hereinafter, each of the configuration devices of the print
system 10 will be individually described.
Print Layer Forming Device
[0112] First, the print layer forming device 40 will be
described.
[0113] The print layer forming device 40 is a device that
discharges the ink 16, which is a fluid, toward the print surface
(that is, an upper surface of the internal scattering member 14b)
of the medium 14 and forms the print layer 17 having a multilayer
structure on the print surface. In the present embodiment, the
print layer forming device 40 is composed of, for example, an
inkjet printer.
[0114] To describe specifically, the print layer forming device 40
sequentially discharges various types of inks 16 toward each unit
region of the print surface (in a strict sense, a range of the
print surface, in which the print layer 17 is formed) of the medium
14. In each unit region, dots of the landed inks form ink layers
and a plurality of ink layers of each ink type overlap each other.
Accordingly, the multilayer structure print layer 17 is formed on
the print surface.
[0115] As shown in FIGS. 1 and 4, the print layer forming device 40
has a control mechanism 42, a moving mechanism 44, and an ink
discharging mechanism 46. The moving mechanism 44 moves the medium
14 along a moving path 44R in the print layer forming device 40. As
shown in FIG. 4, the moving mechanism 44 may be composed of a drive
roller 44a or may be composed of a drive belt.
[0116] From a perspective of further increasing a printing speed,
the moving mechanism 44 is a one-way transporting moving mechanism
that moves the medium 14 only in a forward direction. However,
without being limited thereto, the moving mechanism may be a
reversible transporting moving mechanism that causes the medium 14
to travel reversely to an upstream side by a certain distance after
moving the medium to a downstream side by the same distance along
the moving path 44R and then moves the medium to the downstream
side again.
[0117] The ink discharging mechanism 46 is composed of a recording
head that discharges the various types of inks 16 through the
driving of a piezoelectric element. The ink discharging mechanism
46 discharges the various types of inks 16 toward the print surface
as shown in FIG. 4 while a lower surface thereof faces the print
surface of the medium 14. To describe more specifically, the ink
discharging mechanism 46 is movable in a scanning direction
intersecting a moving direction of the medium 14. In addition, as
shown in FIG. 5, the lower surface of the ink discharging mechanism
46 is a nozzle surface 46S in which a nozzle row is formed for each
ink type. From one end side in the scanning direction, one nozzle
row Nw for discharging a white ink, one nozzle row Ny for
discharging a yellow ink, one nozzle row Nm for discharging a
magenta ink, one nozzle row Nc for discharging a cyan ink, and one
nozzle row Nk for discharging a black ink are provided in the
nozzle surface 46S. However, the number of nozzle rows discharging
various types of inks and disposed positions thereof can be set in
any manner, and a configuration other than the configuration shown
in FIG. 5 may be adopted.
[0118] Then, as the nozzle surface 46S faces the print surface of
the medium 14, the ink discharging mechanism 46 discharges a type
of ink corresponding to each unit region toward each unit region on
the print surface while being moved in the scanning direction at a
position immediately above the print surface by a carriage (not
shown) through a shuttle scanning method. Various types of inks
land on a unit region, which is a discharge destination, and form
dots. As a result, on the surface of the medium 14, the print layer
17, in which the color layer 17a and the white layer 17b are
disposed in an image-wise manner according to the position of each
unit region, is formed.
[0119] As a method of discharging an ink from the ink discharging
mechanism 46, without being limited to the piezoelectric element
drive method, for example, various types of discharge methods can
be used including a thermal jet method of ejecting ink droplets at
the pressure of bubbles generated by heating an ink with a heat
generating body such as a heater. In addition, the ink discharging
mechanism 46 is composed of a serial type head and discharges an
ink under the shuttle scanning method in the present embodiment,
but is not limited thereto. For example, the ink discharging
mechanism 46 is composed of a full-line type head, and may
discharge an ink under a single-pass method. In addition, all
nozzle rows of various types of inks are formed in the same nozzle
surface 46S in the present embodiment, but is not limited thereto.
For example, a configuration where the ink discharging mechanism 46
consists of a plurality of recording heads and the respective
recording heads discharge different types of inks from each other
may be adopted.
[0120] In a case of forming a transparent layer on the print
surface of the medium 14 using a clear ink, it is preferable to
have a hardening mechanism. The hardening mechanism irradiates dots
of the clear ink landed on the print surface of the medium 14 with
light (in a strict sense, ultraviolet rays) and hardens the dots of
the clear ink. The hardening mechanism may be composed of, for
example, a metal highland lamp, a high pressure mercury lamp, and
an ultraviolet ray light emitting diode (LED) and may be disposed
on the downstream side from the ink discharging mechanism 46 in the
moving direction of the medium 14.
[0121] In a case where the hardening mechanism is provided, the ink
discharging mechanism 46 and the hardening mechanism are preferably
disposed to be spaced apart from each other in the moving direction
of the medium 14. However, without being limited thereto, a
configuration where the ink discharging mechanism 46 and the
hardening mechanism are mounted on a common carriage and the ink
discharging mechanism 46 and the hardening mechanism move
integrally in the scanning direction may be adopted. In such a
configuration, it is preferable that the hardening mechanism is
disposed at a position beside the ink discharging mechanism 46, the
hardening mechanism irradiates a clear ink (in a strict sense, the
dots of the clear ink landed on the print surface) with ultraviolet
rays immediately after the ink discharging mechanism 46 has
discharged the clear ink in a single scanning operation.
[0122] The control mechanism 42 is a controller built in the print
layer forming device 40, and controls, via a drive circuit (not
shown), each of the moving mechanism 44 and the ink discharging
mechanism 46 and further each hardening mechanism in a case where
there is the hardening mechanism. To describe more specifically,
the control mechanism 42 receives print data sent from the computer
30. The print data is data indicating forming conditions of the
print layer 17. The print data will be described specifically
later.
[0123] For example, in a case where the predetermined medium 14 is
manually inserted into a substrate introduction port (not shown) of
the print layer forming device 40 immediately after receiving the
print data, the control mechanism 42 controls the moving mechanism
44 such that the medium 14 is picked up and is intermittently moved
along the moving path 44R.
[0124] Next, the control mechanism 42 controls the ink discharging
mechanism 46 in accordance with the print data and causes the ink
discharging mechanism 46 to discharge the ink 16 toward each unit
region of the print surface while the nozzle surface 46S of the ink
discharging mechanism 46 and the print surface of the medium 14
face each other. In this case, the type, amount, and density (dot
density) of the ink 16 landed on each unit region are determined
according to forming conditions indicated by the print data.
[0125] In addition, the control mechanism 42 alternately repeats a
moving operation of the medium 14 by the moving mechanism 44 and a
scanning operation of the ink discharging mechanism 46 and controls
a nozzle that discharges the ink 16 in each scanning operation.
Accordingly, dots of the ink 16 can be formed in an overlapping
manner in the same unit region on the print surface, and for
example, it is possible to adjust the thickness of an ink layer
consisting of the ink 16 by overlapping the dots of the same type
of ink 16. In addition, by overlapping dots of another type of ink
16 on dots of a certain type of ink 16, the multilayer structure
described above is formed.
[0126] Lamination procedures of each ink layer in the multilayer
structure is as described above. For example, at the part 1a
corresponding to the color portion and the part 1c having only the
color portion, the color layer 17a is disposed as an outermost
layer. On the other hand, at the part 1b having no color portion,
the white layer 17b is disposed as an outermost layer.
[0127] In addition, the control mechanism 42 causes the ink
discharging mechanism 46 to discharge the ink 16. In a case where
there is the hardening mechanism, in parallel with this, the
hardening mechanism is controlled and irradiation with ultraviolet
rays is performed. Accordingly, in a unit region where there are
dots of a clear ink, the dots of the clear ink are hardened, and a
transparent layer is formed.
[0128] Then, the control mechanism 42 controls the moving mechanism
44 and the ink discharging mechanism 46 in accordance with the
forming conditions indicated by the print data and controls the
hardening mechanism in a case where there is the hardening
mechanism, and thereby the lamination number of ink layers and the
type and thickness of each ink layer are adjusted for each unit
region. In other words, each portion of the print layer 17 is
formed in an image-wise manner according to the position of each
portion. As a result, the surface texture of the object 12 is
reproduced on the surface (surface on a visible side) of the print
layer 17.
[0129] Then, the medium 14 with the print layer 17 formed on the
print surface, that is, the texture reproduced print 18 is moved to
a discharge port of the print layer forming device 40 by the moving
mechanism 44 and is discharged outside the print layer forming
device 40 from the discharge port.
[0130] In addition, it is possible for the print layer forming
device 40 according to the present embodiment to form sample
patterns SP1 to SP5 shown in FIG. 6 on the medium 14. Each of the
sample patterns SP1 to SP5 consists of an ink layer having only one
color and one layer, and a printed image necessary for the light
scattering measuring device 20 to be described later to measure
internal scattering information (light scattering data) for each
ink type is formed.
[0131] To describe the sample patterns SP1 to SP5, the sample
patterns SP1 to SP5 are formed by gradually changing a dot density
for each of four YMCK colors of inks and a white ink as shown in
FIG. 6. Herein, the dot density means the occupancy rate of dots in
a unit area and in other words, is a pattern concentration
(shading). The dot density is determined by a dot size and the
number of dots in the unit area.
[0132] In a case where the print layer forming device 40 forms each
of the sample patterns SP1 to SP5 on the medium 14, the control
mechanism 42 receives sample pattern forming print data from the
computer 30. Forming conditions (specifically, the position of each
of the sample patterns SP1 to SP5, the type of ink used, and a dot
density) of each of the sample patterns SP1 to SP5 are defined in
the sample pattern forming print data. In a case where the sample
pattern forming print data is received, the control mechanism 42
controls the moving mechanism 44 and the ink discharging mechanism
46 in accordance with the data. Accordingly, for each ink color,
each of the sample patterns SP1 to SP5 is formed on the medium 14
with a dot density gradually changed. The medium 14 used in sample
pattern forming may be the medium 14 for texture reproduction or
may be the medium 14 (for example, white paper) different from the
medium 14 for texture reproduction.
Light Scattering Measuring Device
[0133] The light scattering measuring device 20 measures light
scattering data which is internal scattering information related to
light scattering. In the present invention, a scattering
characteristic of light is represented by the modulation transfer
function (hereinafter, referred to as the MTF).
[0134] Herein, the MTF represents a state of reflected light, in
which the intensity (for example, a brightness value) of light
incident to a thing decreases due to spread caused by subsurface
scattering, as a function, and a vertical axis is the intensity of
light and a lateral axis is a spatial frequency. That is, the MTF
represents the intensity of light with respect to the spatial
frequency of a plurality of types of light having wavelengths
different from each other.
[0135] The light scattering measuring device 20 measures internal
scattering information (light scattering data) indicating light
scattering represented by the MTF. Therefore, the light scattering
measuring device 20 used in the present invention measures the
plurality of types of light having wavelengths different from each
other, specifically, a value of the MTF (MTF data) as internal
scattering information for each of red (R), green (G), and blue (B)
colors of light. In the MTF, the intensity of each of RGB colors of
light at a spatial frequency of 0 represents the intensity of
average color of each color, and thus can be referred to as color
signal information. Therefore, it can be said that the MTF
including the intensity of a period 0 includes color signal
information and internal scattering information.
[0136] To broadly describe a measuring method of MTF data
indicating light scattering, an MTF measuring system in which a
projector camera system is used can be given as an example as
disclosed in Control of translucency by UV printing on translucent
material/Report by the Information Processing Society of Japan,
Vo1.2018-CG-169/No.10 2018/3/3. The MTF measuring system projects a
sine wave pattern from a projector while changing a spatial
frequency in a modulation pattern and images the reflected light
with an RGB camera for each of different frequencies. In this case,
in three RGB channels, a frequency in the modulation pattern is
changed N times from 0 to a predetermined value, and
3.times.N-dimensional MTF data can be obtained.
[0137] In addition, as another measuring method of MTF data, for
example, internal scattering information (light scattering data)
indicating light scattering, which is a measurement target, is
obtained through measurement using a rectangular wave chart LP
shown in FIG. 7. As shown in FIG. 7, the rectangular wave chart LP
is a measurement chart that consists of a plurality of rectangular
patterns LPx formed at predetermined intervals in a transparent
substrate such as a glass plate. In a case of measuring light
scattering, the measurement target and the rectangular wave chart
LP are closely attached to each other, light is incident from a
rectangular wave chart LP side, and reflected light of the
measurement target is measured. In this case, as a result of
transmitted light of the rectangular wave chart LP being scattered
inside the measurement target, an edge portion of the rectangular
pattern LPx is measured to be blurred and slightly darkened.
Qualitatively speaking, this blurring degree indicates light
scattering of the measurement target. In addition, as a method of
quantitatively evaluating the blurring degree, that is, the light
scattering of the measurement target, a method of calculating the
MTF indicating the light scattering can be used.
[0138] A method described in JP2012-205124A is given as an example
of a calculating method of the MTF, but without being limited to
the method described in the same publication, the MTF indicating
light scattering may be acquired through another method.
[0139] For example, the MTF indicating light scattering may be
acquired using a method described in OPTICS LETTERS/Vol. 30, No.
11/Jun. 1, 2005, "Modulated imaging: quantitative analysis and
tomography of turbid media in the special-frequency domain".
[0140] As described above, the light scattering measuring device 20
can measure MTF data of the measurement target as shown in FIG. 8
by measuring the MTF as internal scattering information
representing light scattering of the measurement target using each
of three RGB colors of light. FIG. 8 is a graph showing the MTF
indicating light scattering of the measured measurement target for
each color of light. A lateral axis of FIG. 8 indicates a spatial
frequency, and a vertical axis of FIG. 8 indicates the intensity
(ratio to the intensity of incidence rays) of reflected light.
[0141] Although the MTF represents light scattering and MTF data
indicating the measurement result is measured by the light
scattering measuring device 20 in the present invention, the
present invention is not limited thereto. For example, the light
scattering may be represented by the point spread function (PSF)
indicating point spread of light, and data indicating the
measurement result may be converted into MTF data.
[0142] In the present invention, the light scattering measuring
device 20 measures light scattering with various members as
measurement targets and measures MTF data.
[0143] To describe specifically, the light scattering measuring
device 20 first measures light scattering with respect to the
object of which texture is to be reproduced 12. Accordingly, the
light scattering measuring device 20 measures MTF data
(hereinafter, also referred to as first MTF data) related to the
light scattering with respect to incidence rays to the surface of
the object 12. In the present invention, the surface of the object
12 is divided into a plurality of unit surface regions as described
above, and the light scattering measuring device 20 measures first
MTF data indicating light scattering for each unit surface
region.
[0144] Secondly, the light scattering measuring device 20 measures,
for each of the various types of inks 16 configuring the print
layer 17, MTF data (hereinafter, also referred to as second MTF
data) related to light scattering of the various types of inks 16.
To describe specifically, for example, as described above, the
print layer forming device 40 forms the plurality of sample
patterns SP1 to SP5 by gradually changing a dot density (that is,
by changing a concentration) for each ink 16 including three colors
of YMC inks, a black (K) ink, and a white (W) ink (see FIG. 6). The
light scattering measuring device 20 measures light scattering with
each of the sample patterns SP1 to SP5 as a target. Accordingly,
the light scattering measuring device 20 measures second MTF data
for each type of ink 16 for each density by changing a dot
density.
[0145] Thirdly, the light scattering measuring device 20 measures
light scattering with the surface of the medium 14 for texture
reproduction, specifically, each of a plurality of types of
internal scattering members 14b configuring the medium 14 as a
target. Accordingly, the light scattering measuring device 20
measures MTF data (hereinafter, also referred to as third MTF data)
related to the light scattering of the various types of internal
scattering members 14b. Herein, in a case where parameters that
change according to an internal scattering performance (light
scattering) are different from each other, MTF data is different
between the internal scattering members 14b different from each
other. For example, in a case where Haze values are different from
each other, as the type of the internal scattering member 14b to be
used is changed and a Haze value changes, MTF data representing
light scattering of the texture reproduced print 18 can be
changed.
Computer
[0146] The computer 30 can be said as a printing control device
that causes the print layer forming device 40 to form the print
layer 17 based on MTF data (specifically, the MTF data representing
color signal information and internal scattering information
described above) related to the optical texture of the object 12.
In the present invention, the computer 30 is composed of, for
example, a host computer connected to the print layer forming
device 40.
[0147] On the computer 30, a processor such as a central processing
unit (CPU) and a memory such as a read only memory (ROM) and a
random access memory (RAM) are mounted. In the memory, for example,
an LUT for converting texture characteristic information of the
object 12 into print data for producing the texture reproduced
print 18, a texture reproducing application program for executing
the conversion processing method for optical texture reproduction
of the embodiment of the present invention using the LUT, and a
program such as a printer driver are stored. The computer 30
creates texture reproducing print data for reproducing the optical
texture of the surface of the object 12 as the processor executes
the texture reproducing application program for executing the
method of the embodiment of the present invention using the LUT and
the printer driver.
[0148] In the present invention, in a case of performing LUT
conversion in order to improve the accuracy of color reproduction
in reproducing optical texture, color signal information and
internal scattering information which are included in texture
characteristic information of the object 12 are separately divided
into values of the MTF (MTF data) of a color signal and are used as
input values. Alternatively, a signal value of the perceptual
uniform color space obtained by changing the MTF data of the imaged
color signal, which is the color signal information and the
internal scattering information included in the texture
characteristic information of the object 12, is used as an input
value.
[0149] That is, in the first embodiment of the present invention,
texture characteristic information of the object 12 is separated
into color signal information and internal scattering information,
MTF data is acquired as the color signal information and the
internal scattering information, and the MTF data acquired as the
color signal information and the internal scattering information is
an input for LUT conversion processing using an LUT. For example,
in a case where MTF data of RGB channels is acquired as texture
characteristic information, MTF data of the RGB channels at zero
frequency is separated as color signal information, and MTF data of
the RGB channels at other than zero frequency is separated as
internal scattering information. Then, a ratio of MTF data of color
signal information (RGB) (the MTF data of the RGB channels at zero
frequency) to MTF data of internal scattering information (the MTF
data of the RGB channels at other than zero frequency) is changed
preferably by increasing the weight of the color signal information
and more preferably by increasing the weight of the color signal
information 2 times or more, and the changed ratio is used as an
input for LUT conversion processing. By doing so, granular feeling,
roughness, grayscale inversion, and/or tone jump can be suppressed
in reproducing optical texture, and the accuracy of color
reproduction can be improved.
[0150] On one hand, in the second embodiment of the present
invention, MTF data of the RGB channels of the imaged object 12 is
acquired with texture characteristic information of the object 12
as color signal information and internal scattering information,
the MTF data of the RGB channels is converted or changed into a
signal value of the perceptual uniform color space, and the signal
value of the uniform color space is used as an input for LUT
conversion processing using an LUT. For example, in a case where
the MTF data of the RGB channels is acquired as texture
characteristic information, MTF data of the RGB channels at zero
frequency is acquired as color signal information, and MTF data of
the RGB channels at other than zero frequency is acquired as
internal scattering information. Then, MTF data at all frequencies
existing in the RGB channels is converted into MTF data that is a
signal value of the L*a*b* color space which is the perceptual
uniform color space. Since color signal information is accurately
converted in conversion from the RGB channels into the perceptual
uniform color space such as the L*a*b* color space, granular
feeling, roughness, grayscale inversion, and/or tone jump can be
suppressed in reproducing optical texture, and the accuracy of
color reproduction can be improved.
[0151] On the other hand, texture reproducing print data for
producing the texture reproduced print 18 obtained through LUT
conversion processing is the amounts (CMYKW) of various types of
inks 16 and scattering (S) required for the medium 14. That is, the
amount C of a cyan (C) ink, the amount M of a magenta (M) ink, the
amount Y of a yellow (Y) ink, the amount K of a black (K) ink, the
amount W of a white (W) ink, and a scattering amount of a
scattering layer S of the medium 14 can be given as examples of the
texture reproducing print data.
[0152] As described above, the texture reproducing print data is
data indicating forming conditions of the print layer 17. Herein,
the forming conditions of the print layer 17 is a combination of
parameters that include a layer structure including the presence or
absence of the color layer 17a, the thickness of each ink layer, a
dot density (concentration) in each ink layer, the type of
scattering of the internal scattering member 14b included in the
medium 14 for texture reproduction. A plurality of forming
conditions can be determined by changing each of the parameters
described above, and from the forming conditions, forming
conditions that are actually adopted in a case of forming a print
layer are selected according to the texture of a reproduction
target.
[0153] The forming conditions of the print layer 17 may be any
conditions related to at least one of the parameters, and a
condition related to a parameter other than the parameters may be
included.
[0154] In addition, in the present invention, a print layer formed
range on the print surface of the medium 14 is divided into a
plurality of unit regions, and forming conditions that are actually
adopted in a case of forming the print layer 17 are set for each
unit region.
[0155] The computer 30 creates print data indicating forming
conditions set for each unit region and transmits the print data
toward the print layer forming device 40. In the print layer
forming device 40, the control mechanism 42 receives the print data
and controls each unit of the print layer forming device 40 in
accordance with the print data. Accordingly, the print layer
forming device 40 forms the print layer 17 on the print surface of
the medium 14. In this case, the print layer forming device 40
forms each portion of the print layer 17 in accordance with forming
conditions set with respect to a unit region corresponding to each
portion. Accordingly, each portion of the print layer 17 is formed
in an image-wise manner according to the position of each
portion.
[0156] Next, the conversion processing method using a texture
reproduction conversion LUT will be described.
[0157] FIG. 9 is a diagram showing an example of a flow of LUT
conversion processing using the texture reproduction conversion LUT
used in the present invention.
[0158] In the conversion processing using the texture reproduction
conversion LUT shown in FIG. 9, texture information (light
scattering information for each unit region, that is, each pixel
position) is converted into ink amount information via the LUT.
[0159] First, as shown in FIG. 9, in texture characteristic
information (internal scattering information and color signal
information) acquisition processing S10, for example, the light
scattering measuring device 20 measures, for each unit region of
the object 12, which is a texture reproduction sample, texture
characteristic information, herein, multi-dimensional, that is,
18-dimensional MTF data (first MTF data) at a plurality of
frequencies, in the example shown in FIG. 9, six frequencies
(including zero frequency representing color signal information in
the present invention) for each color channel of the three RGB
channels.
[0160] Next, as shown in FIG. 9, in multi-dimensional information
conversion processing S12, a conversion LUT corresponding to
internal scattering, in which MTF data (internal scattering
information) of the three RGB channels acquired by separating out
MTF data at zero frequency from the 18-dimensional MTF data through
simulation calculation is used as an input value and a combined
condition group of each ink, which consists of ink amount data of
the CMYKW inks 16 and scattering amount data of the scattering
layer (internal scattering member 14b) S of the medium 14, is used
as an output value, is used.
[0161] In this manner, in the multi-dimensional information
conversion processing S12, the MTF data of the three RGB channels
is converted into ink amount data of the CMYKW inks 16 and
scattering amount data of the scattering layer S of the medium 14,
which are forming conditions of the texture reproduced print 18,
using such a conversion LUT.
[0162] In this manner, as shown in FIG. 9, in ink pattern
information acquisition processing S14, print data (the forming
conditions of the texture reproduced print 18) that consists of the
ink amount data of the CMYKW inks 16 and the scattering amount data
of the scattering layer (internal scattering member 14b) S of the
medium 14 is acquired.
[0163] In the present invention, RGBMTF data at zero frequency that
represents color signal information, and RGBMTF data that
represents the other information, which is internal scattering
information, are separated.
[0164] Therefore, also the MTF data of the RGB channels at zero
frequency that represents color signal information is converted
into the forming conditions of the texture reproduced print 18,
which include the ink amount data of each color and the scattering
amount data of the medium 14, using the conversion LUT,
simultaneously for color reproduction with improved accuracy.
[0165] As described above, in the present invention, the color
signal information (MTF data of the three RGB channels at zero
frequency) and the internal scattering information (MTF data of the
three RGB channels at frequencies other than zero) are separately
treated. In this case, a ratio between the color signal information
and the internal scattering information changes in the present
invention, but in order to improve the accuracy of color
reproduction, the weight of the color signal information is
preferably increased, and more preferably increased two times or
more. Alternatively, in LUT conversion, in calculating an error
amount in LUT conversion processing given by a distance from a
lattice point of the LUT, it is preferable to make the weight of an
error amount of the color signal information and the weight of an
error amount of the internal scattering information different from
each other, and it is more preferable to make the weight of the
error amount of the color signal information smaller than the
weight of the error amount of the internal scattering
information.
[0166] Herein, as input values of the conversion LUT, MTF data,
which is the color signal information, and MTF data, which is the
internal scattering information, are preferably weighted data
multiplied by the weight of each ratio. In this case, weighted
addition MTF data obtained by weighting and adding both of weighted
data pieces in a predetermined ratio may be converted through the
conversion LUT, and the ink amount data of each of the CMYKW inks
16 and the scattering amount data of the scattering layer S of the
medium 14 may be acquired to be used as print data for reproducing
the object 12. In addition, each piece of weighted data of the
color signal information and the internal scattering information
may be converted through the conversion LUT, the ink amount data of
each of the CMYKW inks 16 and the scattering amount data of the
scattering layer S of the medium 14 may be acquired, and each of
the acquired ink amount data of each color and the scattering
amount data may be added to obtain print data for reproducing the
object 12.
[0167] Instead of acquiring each piece of weighted data of the MTF
data, which is the color signal information, and the MTF data,
which is the internal scattering information, in advance, each
piece of MTF data may be converted into each piece of the ink
amount data and the scattering amount data of the medium 14, and
the ink amount data and the scattering amount data of the medium 14
after conversion may be weighted in a predetermined ratio and then
each may be added to obtain print data for reproducing the object
12.
[0168] As such a conversion LUT, a conversion LUT stored in the
computer 30 in advance may be used or a conversion LUT may be newly
created each time using the computer 30.
[0169] For example, the conversion LUT can be created as
follows.
[0170] FIG. 10 is a flowchart showing an example of conversion LUT
creation processing of creating a texture reproduction conversion
LUT used in the present invention.
[0171] As shown in FIG. 10, a conversion LUT creating method
consists of sample pattern print processing S20, MTF data
measurement processing S22, light scattering estimation processing
S24, and LUT creation processing S26. The conversion LUT creating
method can be executed using the print system 10 shown in FIG. 1.
Hereinafter, each type of processing will be individually
described.
Sample Pattern Print Processing
[0172] First, the sample pattern print processing S20 is processing
in which the print layer forming device 40 forms the sample
patterns SP1 to SP5 described above on the print surface of the
medium 14. To describe more specifically, the computer 30 transmits
sample pattern forming print data to the print layer forming device
40, and the control mechanism 42 of the print layer forming device
40 receives the print data. The sample pattern forming print data
is created in advance and is stored in the memory in the computer
30.
[0173] The control mechanism 42 controls the moving mechanism 44
and the ink discharging mechanism 46 in accordance with the sample
pattern forming print data and also controls the hardening
mechanism in a case where the hardening mechanism is further
included. Accordingly, on the print surface of the medium 14, the
sample patterns SP1 to SP5 are printed with a dot density
(concentration) gradually changed for each of five colors of inks
including YMCK and W (see FIG. 6). Each of the sample patterns SP1
to SP5 is composed of a plurality of pattern pieces having dot
densities (concentrations) different from each other. Herein,
although it is possible to freely set the number of pattern pieces
configuring each of the sample patterns SP1 to SP5 and a dot
density (concentration) in each pattern piece, in the example shown
in FIG. 6, the number of pattern pieces is four, and a
concentration in each pattern piece is 25%, 50%, 75%, and 100%.
MTF Data Measurement Processing
[0174] The MTF data measurement processing S22 is processing in
which the light scattering measuring device 20 measures the second
MTF data and the third MTF data which are described above. To
describe more specifically, first, the light scattering measuring
device 20 measures MTF data with each of the sample patterns SP1 to
SP5 printed on the medium 14 in the sample pattern print processing
described above as a target. In this case, the light scattering
measuring device 20 measures light scattering (MTF) of each of a
plurality of pattern pieces configuring each of the sample patterns
SP1 to SP5. That is, the light scattering measuring device 20
measures light scattering (MTF) for each dot density by changing a
dot density (concentration) thereof for each of the sample patterns
SP1 to SP5. Accordingly, the light scattering measuring device 20
measures, for each ink type, second MTF data indicating light
scattering for each dot density (concentration).
[0175] Next, the light scattering measuring device 20 measures
light scattering (MTF) of the internal scattering member 14b
included in the medium 14 for texture reproduction. In this case,
in a case where a plurality of types of internal scattering members
14b are prepared, the light scattering measuring device 20 measures
scattering amount data (MTF) of a scattering layer for each of the
various types of internal scattering members 14b. Accordingly, the
light scattering measuring device 20 measures, for each type of
internal scattering members 14b, third MTF data indicating light
scattering of the internal scattering member 14b.
[0176] Then, the light scattering measuring device 20 transmits the
measured second MTF data and the measured third MTF data toward the
computer 30.
Light Scattering Estimation Processing
[0177] The light scattering estimation processing S24 is processing
in which the computer 30 estimates light scattering of the texture
reproduced print 18 according to forming conditions of the print
layer 17 based on second MTF data and third MTF data for each ink
type. Herein, the "light scattering of the texture reproduced print
18 according to forming conditions of the print layer 17" is light
scattering of the texture reproduced print 18 which is generated in
a case where the print layer 17 is tentatively formed under certain
forming conditions.
[0178] In addition, herein, as described above, forming conditions
of the print layer 17 is set for each unit region, and in
accordance with the forming conditions, the light scattering of the
texture reproduced print 18 is estimated for each unit region also
in the light scattering estimation processing S24.
[0179] To describe the light scattering estimation processing S24
specifically, a plurality of forming conditions of the print layer
17 are prepared at the start of the present processing S24.
Specifically, a plurality of combinations are prepared related to a
lamination number of ink layers in the print layer 17, the type of
ink configuring each ink layer, the thickness of each ink layer, a
dot density (concentration) in each ink layer, and the type of the
internal scattering member 14b used in the medium 14 for texture
reproduction.
[0180] After then, the computer 30 executes the light scattering
estimation processing S24 in accordance with the flow shown in FIG.
11.
[0181] FIG. 11 is a flowchart showing an example of a flow of the
light scattering estimation processing shown in FIG. 10. To
describe the flow of the light scattering estimation processing S24
with reference to FIG. 11, the computer 30 first sets a plurality
of combinations related to the forming conditions of the print
layer 17 in Step S30. In Step S30, contents of the forming
conditions described above, specifically, a lamination number of
ink layers configuring the print layer 17, the type of ink
configuring each ink layer, the thickness of each ink layer, a dot
density in each ink layer, and each of types of internal scattering
members 14b are defined as parameters, and each possible
combination of parameters is identified.
[0182] Next, in Step S32, the computer 30 estimates, for each of
the plurality of combinations related to the forming conditions set
in Step S30, light scattering reproduced under the forming
conditions related to the combination.
[0183] In the present invention, since light scattering is
represented by the MTF, in order to estimate an MTF characteristic,
which is light scattering, light scattering analysis calculation is
performed using the combination of the conditions set in Step S30,
second MTF data for each ink type measured for each dot density,
and third MTF data measured for each type of internal scattering
member 14b.
[0184] In the light scattering analysis calculation, the content of
the conditions identified for each unit region in Step S30, the
second MTF data for each ink type, which is measured for each dot
density, and the third MTF data measured for each type of internal
scattering member 14b are applied. As a result, light scattering
(specifically, an MTF characteristic) of each unit region is
calculated. Herein, the MTF characteristic, which is the
calculation result, is an estimation result of light scattering
related to each portion of the texture reproduced print 18, which
is a final product.
[0185] A specific example of the light scattering analysis
calculation described above includes calculation described in
"Kubelka P (1954) New contributions to the optics of intensely
light-scattering materials. Part II: Nonhomogeneous layers. J Opt
Soc Am 44(4):330-335."
[0186] Next, in Step S34, it is determined whether estimation of
light scattering is performed for all of the plurality of
combinations set related to the forming conditions. In a case where
the estimation is not performed, processing returns to Step S30,
and in a case where the estimation is performed, the light
scattering estimation processing S24 is terminated. In this manner,
in the light scattering estimation processing S24, the series of
steps, that is, Steps S30 and S32 of FIG. 11 are repeated for all
of the plurality of combinations set related to the forming
conditions. Accordingly, the light scattering of the texture
reproduced print 18 generated in a case where the print layer 17 is
formed under the forming conditions related to each combination is
estimated by changing combinations.
LUT Creation Processing
[0187] The LUT creation processing is processing of creating an LUT
indicating a correspondence relationship between the plurality of
combinations set related to the forming conditions and the
estimation result of light scattering reproduced under the
conditions related to the combination.
[0188] In a case where the estimation of light scattering is
performed for all of the plurality of combinations set related to
the forming conditions in the previous light scattering estimation
processing S24, the combination related to the forming conditions
and the estimation result of light scattering reproduced under the
conditions related to the combination are associated with each
other, and the correspondence relationship is created by being made
into data as a conversion LUT.
[0189] In this manner, the conversion LUT used in the present
invention can be created.
[0190] The created conversion LUT is referred in the conversion
processing method for texture reproduction of the embodiment of the
present invention to be executed later.
Processing Flow of Texture Reproduced Print Production Including
Processing Flow of Embodiment of Present Invention
[0191] Next, a processing flow of the printed material production
method of producing the texture reproduced print 18 in which the
optical texture of the object 12 is reproduced, that is, a
processing flow of texture reproduced print production including a
processing flow of the conversion processing method for optical
texture reproduction of the embodiment of the present invention
will be described.
[0192] FIG. 12 shows an example of the processing flow of the
texture reproduced print production in which the conversion
processing method of the first embodiment of the present invention
is executed.
[0193] As shown in FIG. 12, the processing flow of the texture
reproduced print production is composed of MTF data measurement
processing S40, MTF data separation processing S42, LUT conversion
processing S44, and print output processing S46. Hereinafter, each
type of processing will be individually described.
MTF Data Measurement Processing
[0194] The MTF data measurement processing S40 is processing of
measuring MTF data representing texture characteristic information
of the object of which texture is to be reproduced 12.
[0195] In the MTF data measurement processing S40, for example, a
color patch 50 and a texture reproduction sample 52 are prepared as
the object of which texture is to be reproduced 12. Herein, the
color patch 50 consists of, for example, four patches having
different concentrations for each of RGB colors and a neutral color
(NC). The texture reproduction sample 52 is, for example, a marble
sample having light scattering.
[0196] Herein, for example, the light scattering measuring device
20 of the print system 10 divides the surface of the color patch
50, which is the object 12, into a plurality of unit surface
regions (one patch), and the light scattering measuring device 20
measures MTF data of the RGB channels representing light scattering
(internal scattering characteristic) of the color patch 50 with
respect to incidence rays to the surface of the color patch 50 for
each unit surface region (each patch). In addition, MTF data for
each unit surface region of the texture reproduction sample 52,
which is the object 12, may also be simultaneously measured.
Accordingly, the light scattering measuring device 20 measures
first MTF data for each unit surface region of the object 12 such
as the color patch 50 and the texture reproduction sample 52.
[0197] In FIG. 12, MTF of the three RGB channels measured at six
frequencies for each patch is represented as six color patches 54,
and the MTF of the three RGB channels of one patch is represented
as a graph 54a and a graph 54b. In the graphs, there is a curve
connecting points indicating intensities at six frequencies
including zero for each of RGB, and the points consist of
18-dimensional MTF data as a whole.
MTF Data Separation Processing
[0198] The MTF data separation processing S42 is processing in
which the computer 30 separates out MTF data of internal scattering
information and MTF data of color signal information which are
included in MTF data of texture characteristic information for each
unit surface region of the object 12.
[0199] MTF data of RGB at zero frequency, which represents the
color signal information, and MTF data at five frequencies other
than zero, which represents only the internal scattering
information, are separated out from 18-dimensional MTF data of the
three RGB channels at six frequencies.
[0200] In FIG. 12, a color patch 56 that includes each of colors of
color patches 56R, 56G, and 56B, which represents MTF data of each
of RGB at zero frequency representing color signal information, and
represents MTF data, and five color patches 58 that represent MTF
data at five frequencies, which are frequencies other than zero and
represent only the internal scattering information, are separately
shown.
LUT Conversion Processing
[0201] The LUT conversion processing S44 is executed by the
computer 30. In the LUT conversion processing S44, first, MTF data
of RGB of color signal information and MTF data of only internal
scattering information, which are separated from each other, are
weighted in a predetermined ratio for each unit surface region.
Next, the MTF data of RGB of the color signal information and the
MTF data of only the internal scattering information, which are
respectively weighted, are respectively LUT-converted, and each of
the amounts CMYKW of inks 16 and the scattering amount of the
scattering layer S of the medium 14 are acquired and finally added
for each color and each scattering amount so that print data is
obtained.
[0202] In FIG. 12, the ink amount data of five types of CMYKW inks
16 after conversion and the scattering amount of the scattering
layer (internal scattering member 14b) S of the medium 14 are shown
by six color patches 60.
[0203] Herein, since it cannot be said that MTF data, which is
measured for each unit surface region, is separated, and becomes an
input value of the LUT, matches MTF data of the RGB channels of the
LUT, closest (an error is smallest) MTF data of an LUT is set as
MTF data to become an input value of the LUT.
[0204] In the LUT, print data corresponding to the set MTF data of
the LUT, that is, the ink amount data of the five types of CMYKW
inks 16, and the scattering amount of the scattering layer
(internal scattering member 14b) S of the medium 14 are acquired.
In this manner, an input value of the MTF data is converted into an
output value of print data.
[0205] As described above, in such LUT conversion, in calculating
an error amount in the LUT conversion processing given by a
distance from a lattice point of the LUT, it is preferable to make
the weight of an error amount of the MTF data of the color signal
information and the weight of an error amount of the MTF data of
the internal scattering information different from each other, and
it is more preferable to make the weight of the error amount of the
color signal information smaller than the weight of the error
amount of the internal scattering information.
[0206] Alternatively, in the LUT conversion, as described above, it
is preferable to make the weight of the color signal information
larger in a ratio between the color signal information and the
internal scattering information.
[0207] In this manner, in a case of LUT-converting the color signal
information, which is color information configuring the texture
characteristic information of the object 12 (the color patch 50 and
the texture reproduction sample 52), and internal scattering
information, the color signal information and the internal
scattering information, which are measured for each unit surface
region, are separated out, LUT conversion is performed by changing
the weights of both of the error amounts to preferably make the
weight of the error amount of the color signal information smaller
or by changing both of the weights to preferably make the weight of
the color signal information larger, and accordingly, print data
(ink amount data of the five types of CMYKW inks 16 and the
scattering amount of the scattering layer (internal scattering
member 14b) S of the medium 14) suitable for reproducing the
texture of the object 12 is acquired for each unit surface
region.
Print Output Processing
[0208] The print output processing S46 is processing of outputting
a color patch print 62, in which the texture of the color patch 50
is reproduced, and a texture reproduced print 64, in which the
texture of the texture reproduction sample 52 is reproduced, based
on the print data obtained in the LUT conversion processing
S44.
[0209] In the print output processing S46, first, the computer 30
transmits the print data set for each unit region toward the print
layer forming device 40.
[0210] Next, the print layer forming device 40 forms (prints) the
multilayer structure print layer 17 on the medium 14 for texture
reproduction in accordance with the print data. Herein, the print
data is created based on the MTF data (specifically, the MTF data
of the color signal information and the internal scattering
information) related to the texture characteristic information of
the object 12 as the computer 30 performs the LUT conversion
processing. Therefore, the print output processing S46 is
processing of forming the print layer 17 on the medium 14 for
texture reproduction based on the print data which is LUT-converted
from the MTF data related to the texture characteristic information
of the object 12.
[0211] In this manner, in texture reproduced print production
processing, in which the conversion processing method of the first
embodiment of the present invention is executed, the texture
reproduced print 18, such as the color patch print 62 and the
texture reproduced print 64, in which the texture of the object 12
such as the color patch 50 and the texture reproduction sample 52
is reproduced with high accuracy, particularly there is no
graininess (roughness) and tone jump generated in reproduction of
texture of the related art, and color reproduction and light
scattering are reproduced with high accuracy, can be output.
[0212] FIG. 13 shows an example of the processing flow of the
texture reproduced print production in which the conversion
processing method of the second embodiment of the present invention
is executed.
[0213] As shown in FIG. 13, the processing flow of the texture
reproduced print production is composed of the MTF data measurement
processing S40, Lab conversion processing S48, LUT conversion
processing S50, and the print output processing S46. Hereinafter,
each type of processing will be individually described. However,
since the MTF data measurement processing S40 and the print output
processing S46 are the same as the steps in the processing flow of
the texture reproduced print production shown in FIG. 12, detailed
description thereof will be omitted.
MTF Data Measurement Processing
[0214] As described above, the MTF data measurement processing S40
is processing of measuring, for each unit surface region, the MTF
data representing the texture characteristic information of the
object of which texture is to be reproduced 12.
[0215] In the MTF data measurement processing S40, as described
above, for example, the MTFs of the color patch 50 and the texture
reproduction sample 52 are measured as the object of which texture
is to be reproduced 12, and are obtained as the six color patches
54 which are MTFs measured at six frequencies for each of the three
RGB channels for each patch.
Lab Conversion Processing
[0216] The Lab conversion processing S48 is processing in which the
computer 30 converts a value of MTF data of the three RGB channels
of the internal scattering information and the color signal
information that are included in the texture characteristic
information of the object 12, which is obtained by imaging the
object 12, into a signal value of the perceptual uniform color
space, that is, the L*a*b* color space.
[0217] In the Lab conversion processing S48, conversion from
18-dimensional MTF data of the three RGB channels at six
frequencies into six types of MTF data of L*, which represents
lightness, and six types of MTF data of each of chromaticity a* and
chromaticity b*, which indicate color tone and chroma saturation
respectively, is performed.
[0218] In FIG. 13, the six types of MTF data of L* are represented
by six color patches 66L, the six types of MTF data of chromaticity
a* are represented by six color patches 66a, and the six types of
MTF data of chromaticity b* are represented by six color patches
66b.
[0219] The six types of MTF data of each of L*, chromaticity a*,
and chromaticity b* correspond to six frequencies respectively, and
MTF data at zero frequency, which represents the color signal
information, and five frequencies, which are frequencies other than
zero and represent only the internal scattering information, are
included therein.
[0220] In the Lab conversion processing S48, since a value of MTF
data of the three RGB channels is converted into a signal value of
the perceptual uniform color space (for example, the L*a*b* color
space), color reproduction is reliably performed, and reproduction
of light scattering (internal scattering information) is unlikely
to be affected also in the subsequent LUT conversion processing
S50. Thus, color reproduction and light scattering are reproduced
in the texture reproduced print 18 with high accuracy.
LUT Conversion Processing
[0221] The LUT conversion processing S50 is executed by the
computer 30 like the LUT conversion processing S44 shown in FIG.
13. In the LUT conversion processing S50, first, three types of MTF
data, including the MTF data of L*, the MTF data of a*, and the MTF
data of b*, which include the color signal information and the
internal scattering information, are LUT-converted for each unit
surface region, and print data that consists of the amounts CMYKW
of inks 16 and the scattering amount of the medium 14 is
obtained.
[0222] Also in FIG. 13, as in the case of FIG. 12, the ink amount
data of the five types of CMYKW inks 16 after conversion and the
scattering amount of the scattering layer (internal scattering
member 14b) S of the medium 14 are shown by the six color patches
60.
[0223] Herein, since it cannot be said that MTF data, which is
measured for each unit surface region, is separated, and becomes an
input value of the LUT, matches the three types of MTF data of the
L*a*b* color space of the LUT, closest (an error is smallest) MTF
data of the LUT is set as the MTF data to become the input value of
the LUT.
[0224] In the LUT, print data corresponding to the set MTF data of
the LUT, that is, the ink amount data of the five types of CMYKW
inks 16, and the scattering amount of the scattering layer
(internal scattering member 14b) S of the medium 14 are acquired.
In this manner, an input value of the MTF data is converted into an
output value of print data.
[0225] In this manner, by LUT-converting the three types of MTF
data of the L*a*b* color space including the color signal
information and the internal scattering information, which
configure the texture characteristic information of the object 12
(the color patch 50 and the texture reproduction sample 52), print
data (ink amount data of the five types of CMYKW inks 16 and the
scattering amount of the scattering layer (internal scattering
member 14b) S of the medium 14) suitable for reproducing the
texture of the object 12 is acquired for each unit surface
region.
Print Output Processing
[0226] The print output processing S46 is processing of outputting
the color patch print 62, in which the texture of the color patch
50 is reproduced, and the texture reproduced print 64, in which the
texture of the texture reproduction sample 52 is reproduced, based
on the print data obtained in the LUT conversion processing
S50.
[0227] The print output processing S46 shown in FIG. 13 is
different from the print output processing S46 shown in FIG. 12 in
that print data is obtained in the LUT conversion processing S50,
but is the same in that print data becomes an input, thereby being
performed in the same manner.
[0228] In this manner, even in a case where the conversion
processing method of the second embodiment of the present invention
is executed, as in the case of the first embodiment, the texture
reproduced print 18, such as the color patch print 62 and the
texture reproduced print 64, in which the texture of the object 12
such as the color patch 50 and the texture reproduction sample 52
is reproduced with high accuracy, particularly there is no
graininess (roughness) and tone jump generated in reproduction of
texture of the related art, and color reproduction and light
scattering are reproduced with high accuracy, can be output.
[0229] Next, in the present invention, reasons why problems such as
graininess, particularly granular feeling (roughness), grayscale
inversion, and/or tone jump generated in reproduction printing of
the related art are solved, reproduction of color reproduction,
which is an important element of texture, is good, and color
reproduction and light scattering can be reproduced with high
accuracy will be described.
[0230] FIG. 14 shows an example of a graph of the MTF indicating an
LUT using method for optical texture reproduction of the embodiment
of the present invention. On the other hand, FIG. 15 shows an
example of a graph of the MTF indicating an LUT using method of the
related art for optical texture reproduction.
[0231] In the graph of the MTF shown in FIG. 15 of the related art,
with respect to a graph of a target MTF, which is close to the
intensity of 1 at zero frequency indicating an average color,
decreases as going toward high frequencies, and is indicated by a
solid line, an approximate MTF by an ink, which is substantially
constant at the intensity of approximately 0.5 from zero frequency
to a high frequency and is indicated by a dotted line, is selected
as an MTF in reproduction printing.
[0232] However, in the graph of the MTF, an error of intensity at
zero frequency representing an average ink color is large as 0.5,
the error with respect to the ink average color is large, and a
color difference is remarkably visible as described above.
[0233] On the contrary, in the present invention, with respect to
the graph of the target MTF, which is indicated by the solid line,
the approximate MTF by an ink, which is close to the intensity of 1
in the period 0 from period 0 to a high frequency, which indicates
the average color, is substantially constant, and is indicated by
the dotted line, is selected as the graph of the MTF in
reproduction printing.
[0234] As a result, an error with respect to the ink average color
in the reproduction printing is small, and a visible color
difference is reduced. On the other hand, on a frequency space,
that is, on the graph, an error of a high frequency portion
indicating the spread of light seems to be large. However, since
the MTF of the ink has not changed as a ratio to zero frequency, in
the real space, a difference visible to the human eye, which is a
light scattering deviation amount, that is, a difference in a light
spread distance is approximately the same.
[0235] Therefore, in the present invention, reproduction of color
reproduction, which is an important element of texture, is good,
and color reproduction and light scattering can be reproduced with
high accuracy.
[0236] Herein, the MTF used in the present invention will be
supplementally described.
[0237] First, as shown in FIG. 16, the MTF shows the spread of a
point image of light incident to one point of an object in a
frequency space, and is written as intensity (amplitude), such as a
brightness value and reflectivity with respect to a frequency.
Similarly, the MTF is an absolute value of the point spread
function (PSF), which shows the spread of the point image of the
light incident to the one point of the object in the real space and
is expressed in a frequency region.
[0238] In the graph of the MTF shown in FIG. 16, a portion
surrounded by a circle, in which the frequency is 0, represents an
average value. Therefore, the portion where the frequency is 0
represents an average color of RGB in a case of the MTF of colors
such as RGB. In addition, in a case of the MTF of the L*a*b* color
space, the portion where the frequency is 0 represents average
lightness in a case of L*, and indicates average color tone and
average chroma saturation in a case of a*b*.
[0239] As shown in (A) and (B) of FIG. 17, in two different graphs
of MTFs, which are indicated by a dotted line and a solid line in
the frequency space shown in (A) of FIG. 17, the dotted line is on
an outer side, but in two different graphs of PSF, which are
indicated by a dotted line and a solid line in the real space shown
in (B) of FIG. 17, the solid line is on the outer side. A
relationship with the spread in both graphs is reverse. That is, it
can be said that a relationship of half-width (spread) is reversed
between the frequency space and the real space.
[0240] Therefore, as shown in FIG. 18, since half-widths of two
different graphs of the MTFs, in which the intensity is maximum at
a portion where the frequency is 0 and the intensity decreases
toward a high frequency, almost match each other, it can be said
that a degree (distance) of light scattering is almost the same in
the real space as can be seen from (A) and (B) of FIG. 17.
[0241] In addition, as shown in FIG. 19, in two different graphs of
the MTFs, in which maximum intensities are different from each
other at a portion where the frequency is 0 but the intensities
similarly decrease toward a high frequency, since half-widths
themselves almost match each other while intensities at which the
half-widths are taken are different from each other, it can be said
that a degree (distance) of light scattering is almost the same in
the real space as can be seen from (A) and (B) of FIG. 17.
[0242] From the above, it can be seen that color reproduction can
be improved without deteriorating light scattering in the real
space by giving the color signal information (MTF data) priority
over the internal scattering information (MTF data) in the
frequency space (MTF data), in a case of LUT-converting the
internal scattering information and the color signal information,
which are included in the texture characteristic information of the
object, in the present invention.
[0243] Although various embodiments and examples of the conversion
processing method for optical texture reproduction according to the
embodiments of the present invention have been described in detail
hereinbefore, the present invention is not limited to the
embodiments and the examples, and it is evident that various
improvements or changes may be made without departing from the gist
of the present invention.
EXPLANATION OF REFERENCES
[0244] 1a, 1b, 1c: part [0245] 10: print system [0246] 12: object
of which texture is to be reproduced (object) [0247] 14: medium
[0248] 14a: white medium [0249] 14b: internal scattering member
[0250] 16: ink [0251] 17: print layer [0252] 17a: color layer
[0253] 17b: white layer [0254] 18, 64: texture reproduced print
[0255] 20: light scattering measuring device [0256] 30: computer
[0257] 40: print layer forming device [0258] 42: control mechanism
[0259] 44: moving mechanism [0260] 44a: drive roller [0261] 44R:
moving path [0262] 46: ink discharging mechanism [0263] 46S: nozzle
surface [0264] 50, 54, 56, 56R, 56G, 56B, 58, 60, 66L, 66a, 66b,
70: color patch [0265] 52: texture reproduction sample [0266] 54a,
54b: graph of MTF [0267] 62, 72: color patch print [0268] 72a:
region [0269] 74: reproduced image print [0270] LP: rectangular
wave chart [0271] LPx: rectangular pattern [0272] Nc, Nm, Ny, Nk,
Nw: nozzle row [0273] SP1, SP2, SP3, SP4, SP5: sample pattern
* * * * *